Imaging lens
An imaging lens which uses a larger number of constituent lenses for higher performance and features a low F-value, low-profile design and a wide field of view. Designed for a solid-state image sensor, the imaging lens includes constituent lenses arranged in order from an object side to an image side: a first positive refractive power lens; a second negative refractive power lens; a third lens; a fourth lens; a fifth lens; a sixth lens having a concave image-side surface near an optical axis; and a seventh negative refractive power lens.
1. An imaging lens, comprising, in order from an object side to an image side thereof:
a first lens with positive refractive power;
a second lens;
a third lens;
a fourth lens;
a fifth lens;
a sixth lens with negative refractive power that is a double-sided aspheric lens;
a seventh lens that is a double-sided aspheric lens having an image-side surface that is concave near an optical axis of the imaging lens, the image-side surface of the seventh lens having a pole-change point separated from the optical axis,
wherein conditional expressions (5) and (6) below are satisfied:
0.6< TTL/ 2 ih< 1.0 (5)
0.85<Σ d/f< 1.25 (6)
where:
TTL: distance along the optical axis from an image plane of the imaging lens to an object-side surface of an optical element located nearest an imaged object,
ih: maximum image height,
f: overall focal length of the imaging lens, and
Σd: distance along the optical axis from an object-side surface of the first lens to the image-side surface of the seventh lens.
2. The imaging lens according to claim 1 , wherein the object-side surface of the first lens is convex near the optical axis, and the second lens has negative refractive power and an image-side surface that is concave near the optical axis.
3. The imaging lens according to claim 2 , wherein conditional expressions (8) and (9) below are satisfied:
0.7< f 1/ f< 1.5 (8)
−5.0< f 2/ f<− 1.0 (9)
where
f1: focal length of the first lens, and
f2: focal length of the second lens.
4. The imaging lens according to claim 1 , wherein the third lens has positive refractive power and an image-side surface that is convex near the optical axis, and the fourth lens has negative refractive power and an image side surface that is concave near the optical axis.
5. The imaging lens according to claim 4 , wherein conditional expression (11) below is satisfied:
0.6< f 5/ f< 1.2 (11)
where
f5: focal length of the fifth lens.
6. The imaging lens according to claim 1 , wherein the fifth lens is a meniscus lens having positive refractive power and an image-side surface that is convex near the optical axis.
7. The imaging lens according to claim 1 , wherein the sixth lens is a meniscus lens having an image-side surface that is concave near the optical axis and a pole-change point separated from the optical axis on each of an object-side surface and the image-side surface thereof, and the seventh lens has negative refractive power.
8. The imaging lens according to claim 7 , wherein conditional expression (12) below is satisfied:
−1.2< f 67/ f<− 0.6 (12)
where
f67: composite focal length of the sixth lens and the seventh lens.
9. The imaging lens according to claim 1 , wherein conditional expressions (1) and (2) below are satisfied:
50<ν d 1<70 (1)
20<ν d 2<30 (2)
where
νd1: Abbe number of the first lens at d-ray, and
νd2: Abbe number of the second lens at d-ray.
10. The imaging lens according to claim 1 , wherein conditional expressions (3) and (4) below are satisfied:
50<ν d 3<70 (3)
20<ν d 4<30 (4)
where
νd3: Abbe number of the third lens at d-ray, and
νd4: Abbe number of the fourth lens at d-ray.
11. The imaging lens according to claim 1 , wherein a conditional expression (7) below is satisfied:
0.8< ih/f< 1.2. (7)
12. The imaging lens according to claim 1 , wherein a conditional expression (10) below is satisfied:
2.0<| f 34/ f| (10)
where
f34: composite focal length of the third lens and the fourth lens.
13. The imaging lens according to claim 1 , wherein conditional expressions (13), (14), and (15) below are satisfied:
50<ν d 5<70 (13)
20<ν d 6<30 (14)
50<ν d 7<70 (15)
where
νd5: Abbe number of the fifth lens at d-ray,
νd6: Abbe number of the sixth lens at d-ray, and
νd7: Abbe number of the seventh lens at d-ray.
14. The imaging lens according to claim 13 , wherein conditional expressions (1) and (2) below are satisfied:
50<ν d 1<70 (1)
20<ν d 2<30 (2)
where
νd1: Abbe number of the first lens at d-ray, and
νd2: Abbe number of the second lens at d-ray.
15. An imaging lens, comprising, in order from an object side to an image side thereof:
a first lens with positive refractive power;
a second lens;
a third lens;
a fourth lens;
a fifth lens;
a sixth lens that is a double-sided aspheric lens having an image-side surface that is concave near an optical axis of the imaging lens, one of an object-side surface and the image-side surface of the sixth lens having a pole-change point separated from the optical axis; and
a seventh lens that is a meniscus double-sided aspheric lens having an image-side surface that is concave near the optical axis, the image-side surface of the seventh lens having a pole-change point separated from the optical axis,
wherein conditional expressions (5) and (6) below are satisfied:
0.6< TTL/ 2 ih< 1.0 (5)
0.85<Σ d/f< 1.25 (6)
where
TTL: distance along the optical axis from an image plane of the imaging lens to an object-side surface of an optical element located nearest an imaged object,
ih: maximum image height,
f: overall focal length of the imaging lens, and
Σd: distance along the optical axis from an object-side surface of the first lens to the image-side surface of the seventh lens.
16. The imaging lens according to claim 15 , wherein the object-side surface of the first lens is convex near the optical axis, and the second lens has negative refractive power and an image-side surface that is concave near the optical axis.
17. The imaging lens according to claim 15 , wherein the third lens has positive refractive power and an image-side surface that is convex near the optical axis, and the fourth lens has negative refractive power and an image-side surface that is concave near the optical axis.
18. The imaging lens according to claim 15 , wherein the fifth lens is a meniscus lens having positive refractive power and an image-side surface that is convex near the optical axis.
19. The imaging lens according to claim 15 , wherein the sixth lens is a meniscus lens having a pole change point separated from the optical axis on each of the object-side surface and the image-side surface thereof, and an object-side surface of the seventh lens is convex near the optical axis and has a pole-change point separated from the optical axis.
20. The imaging lens according to claim 15 , wherein a conditional expression (5) below is satisfied:
0.6< TTL/ 2 ih< 1.0 (5).